Reconfiguring the logging infrastructure with a per-test output file mimicks
the behavior of per-test output (log output captured only on failures) while
still using the normal logging code, which is important for benchmarking.
To enable this behavior, the ARTIFACT env variable must be set.
It needs to be set twice, once for ktesting+klog, once for
component-base/logs. The latter was not done before and thus quite a bit of log
output was produced with verbosity 0.
By parsing flags in the test's main function before starting etcd we bail out
early without ever starting etcd when the test was invoked with -help.
Otherwise etcd must be available, gets started and then hangs because
flag.Parse itself exits when called by testing.go. This bypasses the code in
EtcdMain which normally stops etcd.
